Authors
H Chapman1; 1 University of Arkansas, United States Discussion
Drug resistance occurs wherever livestock are raised under intensive conditions and drugs are used to combat parasitic infections. This is particularly true for the agents used for the prevention of coccidiosis caused by protozoa of the genus Eimeria in poultry. Resistance has been documented for all the drugs approved for use in chickens and varying levels of resistance is present for those currently employed. A solution may be the introduction of drug-sensitive parasites into houses where poultry are raised so that they may replace drug-resistant organisms. This can be achieved by utilizing vaccines that contain strains of Eimeria that were isolated before drugs were introduced. Such strains are inherently drug-sensitive. In this report we provide evidence to support this contention. Five flocks of broilers were reared in pens and given drug programs followed by vaccination. Parasites were isolated following the fifth flock and results showed that sensitivity to a widely used drug had been restored. A proposal for a yearly broiler production cycle involving chemotherapy and vaccination is presented. There are few, if any, examples in veterinary parasitology where it has proved possible to restore sensitivity to drugs used to control a widespread parasite. 
